How do I get rid of nsappshell:eventwindow, and get my Task Manager back to where I can see it?

2-3 weeks ago, my Task Manager quit showing itself except for a line on the bottom.
And once as I was shutting down, I had to end the aforementioned file.
My computer gets hung up for short periods occasionally, and sometimes, runs slower.

2-3 weeks ago, my Task Manager quit showing itself except for a line on the bottom.
And once as I was shutting down, I had to end the aforementioned file.
My computer gets hung up for short periods occasionally, and sometimes, runs slower.

Did you try to drag up the taskbar with the left mouse key pressed in case you've hidden it?
Try to use "Firefox/File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") to close Firefox if you are currently doing that by clicking the close X on the title bar.
See also:
*"Hang at exit": http://kb.mozillazine.org/Firefox_hangs
*"Firefox hangs when you quit it": https://support.mozilla.org/kb/Firefox+hangs